This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Spider silks have the potential to provide new bio-inspired materials for numerous applications in bioenergetics and products ranging from protective clothing to artificial ligaments and tendons. Current efforts are focused on mimicking spider silk through synthetic proteins. In the past several years we have used recombinant DNA methods to generate synthetic spider silk proteins. We now have over 20 different proteins which vary in the ratio of crystalline to amorphous regions as well as the protein sequences in both of those regions. Most of these have been spun into fibers and these fibers range in mechanical properties from those with elasticities and toughness values greater than dragline silk to those with values much less than the natural silks. The molecular basis for these differences cannot be determined using current methods. Here we propose to use x-ray fiber and microdiffraction at Argonne National Labs (ANL) Advanced Photon Source (APS). Specifically the x-ray station at beam-line sector 14 has been optimized for biological fiber diffraction and provided unprecedented sensitivity for spider silk fiber diffraction. We propose to run a series of spider dragline silk standards both wet and dry as well as our new series of transgenic silkworm cocoon producing spider silk fibers. The x-ray diffraction at sector 14 (14-BM-C- BIOCARS with Dr. R. Henning) is critical to characterizing the structure of these important biopolymer fibers.